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\begin{tabular}{cccc}
Tahoe & 20 & 30 & 40 \\
Utah & 10 & 30 & 60 \\
Colorado & 10 & 40 & 50
\end{tabular}

a. [tex]$df=$[/tex] [tex]$\square$[/tex] 2

b. What is the [tex]$\chi^2$[/tex] test statistic? [tex]$\square$[/tex]

c. What is the [tex]$p$[/tex]-value? If your answer is less than .01, write 0. [tex]$\square$[/tex]

d. Do we reject the null hypothesis at [tex]$\alpha=.05$[/tex]?

[tex]$\rightarrow$[/tex] A. Yes

B. No

Sagot :

To solve this problem, let's go through it step-by-step using the information provided.

### Part a: Degrees of Freedom (df)

The degrees of freedom in a chi-square test for independence is calculated using the formula:
[tex]\[ \text{df} = (r - 1) \times (c - 1) \][/tex]
where [tex]\( r \)[/tex] is the number of rows and [tex]\( c \)[/tex] is the number of columns in the contingency table.

The provided table has 3 rows (Tahoe, Utah, Colorado) and 3 columns (not labeled but there are three data points in each row). So:
[tex]\[ \text{df} = (3 - 1) \times (3 - 1) = 2 \times 2 = 4 \][/tex]

So, the degrees of freedom is:
[tex]\[ \boxed{4} \][/tex]

### Part b: Chi-Square Test Statistic ([tex]\(\chi^2\)[/tex] statistic)

The chi-square test statistic provided is:
[tex]\[ \chi^2 \approx 10.5259 \][/tex]

So, the chi-square test statistic is:
[tex]\[ \boxed{10.5259} \][/tex]

### Part c: p-Value

The given p-value is:
[tex]\[ p \approx 0.0324 \][/tex]

As the p-value is greater than 0.01, we don't need to write 0.

So, the p-value is:
[tex]\[ \boxed{0.0324} \][/tex]

### Part d: Decision at [tex]\(\alpha = 0.05\)[/tex]

To decide whether to reject the null hypothesis, compare the p-value to the significance level ([tex]\(\alpha = 0.05\)[/tex]).

The rule is:
- If [tex]\( p < \alpha \)[/tex], reject the null hypothesis.
- If [tex]\( p \geq \alpha \)[/tex], do not reject the null hypothesis.

Given [tex]\( p \approx 0.0324 \)[/tex], which is less than [tex]\( 0.05 \)[/tex]:
[tex]\[ 0.0324 < 0.05 \][/tex]

Therefore, we reject the null hypothesis at [tex]\(\alpha = 0.05\)[/tex].

So, the answer is:
[tex]\[ \boxed{\rightarrow \odot \text{A. Yes}} \][/tex]

In summary:
- Degrees of freedom: [tex]\(\boxed{4}\)[/tex]
- Chi-square test statistic: [tex]\(\boxed{10.5259}\)[/tex]
- p-value: [tex]\(\boxed{0.0324}\)[/tex]
- Reject the null hypothesis at [tex]\(\alpha = 0.05\)[/tex]? [tex]\(\boxed{\rightarrow \odot \text{A. Yes}}\)[/tex]